The melting plants or re-melting plants, respectively, which are known in practice comprise mainly a supporting construction having a frame, a framework, a gantry, or a pillar, and a gas protection hood in the form of a gas-tight cylinder, a lead through in the upper end of the gas protection hood, an electrode rod which by way of the lead through is introduced into the gas protection hood in a pressure-tight or vacuum-tight manner, and a drive unit which moves the electrode rod vertically upwards or downwards in the gas protection hood. One or two melting stations in which the re-melting process of the electrode suspended from the electrode rod takes place are provided. A weighing installation is used for regulating the process.
Re-melting plants which are conceived such that the re-melting process can take place at an elevated gas pressure in the hood as well as at a reduced pressure such as, in particular, a vacuum, are known in practice. It is specifically in the case of these re-melting plants in which the re-melting process is carried out at a gas pressure which differs from the atmospheric pressure that there is the problem that an additional force which in the case of positive pressure under the hood can be referred to as an ejection force and in the case of a vacuum under the hood can be referred to as an intake force acts on the electrode rod. In a manner corresponding to the concept of the plant and the concept of the electrode rod drive of the plant, said force acts on the drive elements of the electrode rod such that said drive elements are not only stressed by the weight of the electrode but additionally also by said intake or ejection force. This stress is particularly dangerous when the re-melting process is carried out at an elevated gas pressure and the vertical movement of the electrode rod is performed by way of a drive spindle which is disposed in a coaxial manner in the electrode rod. The risk of buckling is to be mentioned specifically. In the case of the known embodiments, a spindle with a very large diameter is used so that said spindle can resist the buckling that may be caused by a corresponding ejection force.